Dragons' Den star Duncan Bannatyne has pledged to do everything in his power to ensure a blackmailer targeting his daughter is caught.

Police are investigating after threats were made via email and on Twitter.

The 62-year-old entrepreneur, philanthropist and author used Twitter to offer a £30,000 reward for information leading to the arrest of the person involved.

Durham Police said the threats appear to originate from an email address based in Russia.

A spokesman for the force said: "Durham Constabulary can confirm Duncan Bannatyne has reported a number of threatening messages he had received via email and Twitter in which threats were made against a member of his family. These appeared to originate from an email address based in Russia. We have been liaising since then with Mr Bannatyne and conducting inquiries into the credibility of these threats."

Bannatyne, who was born in Clydebank, Scotland, but whose business is based in Darlington, issued a statement which said: "My family is well protected but I take any threat to them very seriously and will do all I can to ensure the person or people involved are caught."

Reports said that Bannatyne had deleted tweets after offering a £50,000 reward for anyone who broke the arms of the man issuing the threats.

They said that someone calling himself Yuri Vasilyev tweeted Bannatyne three days ago, saying: "I'm looking for a £35,000 investment to stop us hurting your Hollie Bannatyne. We will bring hurt and pain into your life. We are watching her. She is very attractive. Want photos?"

Bannatyne is said to have told his more than 350,000 Twitter followers: "I offer £25,000 reward for the capture of the coward who calls himself @YuriVasilyev_ Double if his arms are broken first." He added: "I am serious btw (by the way). I think he is in Moscow."

Some Twitter users criticised him for appearing to solicit violence, and he then deleted the tweets and changed his offer to "£30,000 reward for info leading to his arrest", the reports said.